Variable resistance



Sept. 22, 1931. E. R. STOEKLE 1,824,242

VARIABLE RB 51 S TANG E Filed June 11, 1927 2 Sheets-Sheet 1 INVENTOR.

A TTORNE Y.

P 1931. E. R. STOEKLE 1 1,824,242

VARIABLE RESISTANCE Filed June 11,, 1927 2 Sheets-Sheet 2 INVENTOR. By 6A, M

7km M W A TTORNE Y.

Patented Sept. 22, 1931 UNITED STATES PATENT OFFICE EBWIN n. S'IOEKLE,or MILWAUKEE, WISCONSIN, ASSIGNOB 'ro CENTRAL RA IO LABORATORIES, orMILWAUKEE, WISCONSIN, A CORPORATION 01? WISCONSIN VARIABLE RESISTANCEApplication filed June 11,

This invention relates to a variable resistance adapted for use as arheostat or as a single or double potentiometer.

In variable resistances of this character as heretofore proposed theresistance element or resistor was mounted on an insulating base in theform of a disk or panel, and this same insulating base was constructedand equipped to serve as a' support for the shaft or'arbor carrying thecontact shoe cooperable with the resistor. Such a construction isrelatively heavy, awkward to handle and mount, and is not onlycomplicated and more or less difficult to produce, especially as regardsits assembly, but is also comparatively expensive.

One of the objectsof the present invention resides in the elimination ofthe insulating base and the avoidance of the disadvantages incident tothe production and use thereof.

In carrying out the present invention, the resistor is mounted on andinsulated from a a s lit core, usually annular in form, and the sliaftor arbor carrying the contact shoe is supported from the core of theresistor. Preferably, the shaft or arbor is supported in a bearmgprovided at the inner end of a radial arm, the outer end of which radialso arm is firmly and rigidl secured to lugs integral with the ends 0 theannular core located at the split provided therein. The lugs which thusserve as a convenient means for fastening the arm to the core, also pro-'vide a convenient mounting means for the bindingposts employed toconnect the contact shoe and the resistor with the circuits or theinstrumentalities with which they are associated. Usually two bindingposts are '9 -mounted on the lugs of the core, but provision is made forthe mounting of a third binding post on an extension of the arm. B biiidn'g posts theresistance may be utilized as a rheostat, in which caseonly two binding posts are utilized, or may be employed as apotentiometer, in which event all three binding posts are employed. Thecontact shoe employed when the device is utilized asa rheostat or as apotentiometercoacts providing for the mounting of three 1927. Serial No.198,014.

with the bends of the turns of the resistor located around one edge ofthe core. By employing a second contact shoe insulated from the arborthough mounted thereon and located to coact with the bends of the turnsat the opposite edge of the core, the resitsor may also be employed as adouble potentiometer. The arm which supports the sleeve receiving theshaft or arbor for the contact shoe of the rheostat or potentiometerpreferably has bendable lugs integral there-' ing one embodiment of theinvention whenused as a rheostat;

Figure 2 is a view in section taken on line 22 of Figure 1;

'Figures 3, 4, and 5 are detail sectional views taken on lines 33, 44and 5-5 respectively of Figure 1;

Figure6 is a View in rear elevation showing the device adapted for useas a potentiometer;

Figure 7 is a fragmentary detail sectional view taken on line 7--7 ofFigure 6 with parts shown in elevation for the sake of illustrationFigure 8 is a similar view taken on line 8-8 of Figure 7 Figure 9 is aview in rear elevation illustrating the device when used as a grid bias,as well as a rheostat or potentiometer;

Figure 10 is a sectional view taken on line 10-10 of Figure 9;

Figure 11 is a detail perspective view of the core;

Figure 12 is a similar view of the arm;

Figure 13 is a similar View of the contact shoe employed for the gridbias; and

Figure 14 is a detail View in elevation of the sleeve supported at theinner end of the arm and adapted to receive the arbor or haft- Referringto the drawings, it will be seen that in all embodiments of theinvention a split annular core 1 is provided the core 1 beingconstituted of 'metalWvh-i-ch isv an electrical conductor and which is-s-uifici-ently bendable to permit it to be shaped. as described,although in the assembly the core is substantially rigid. outwardlydirected lugs 2are provided. In between the lugs ,2 theouter end of aradial connecting and supponting arm 3 is positioned and firmly andsecurely fastened any suitable wa n for instance, by weld-- ing, andalso by the action-of the tastenmg means for the binding posts to be*l-ater idescribed. The arm '3- is doubled upon itself and at its innerend has a bight 4 shaped to receive and. embnacea bearing sleeve 5. The

. sections-of the armS-aresecnred together by a spot weld 6i, and thisspot weldhas been tound sufiicient to cause the bight portion 4;o-f-thearmtocl'aanp and firmly grip the pent-ion of the sleevefittedthere-inwhere the sleeve 5 isfixed to the arm. A shaft or arbor 7'is rotatably fitted in the sleeveshownin Figures .2 and the shaft 7 has.a shoulder 8 limiting, enidwise movement-ot-the arbor Z inthe sleeve.5. in one direction. Endwi-se movement of the arbor 7 in anopposite-direction is prevented by the action of a contact shoe 9"secured as at 10,130 the endof the argbor opposite the shoulder 8. Thiscontact shoe 9' is somewhat re silient is tensioned to engage or pressagainst the resistance element or resistor 11 which consists of a wirewrapped around.

insulation .12coverin-g the core 1. The turns of the Wire 11 are spacedfrom each. other and the contact shoe 9:;coacts with thebends 11 of theturns located around one edge of the insulation covered core.Tofacilitate the sliding adjustment of the contact shoe 9 over the turnsof the resistor. 11, the edgeportionsof the contact shoe which engagethe resistor are deflected or beveled as indicated 21179 in. Figure 5;

When the-device is employed as a rheostat,

one end of the wire- '11 is connected to binding post designatedgenerally at ,13.

The binding post 13 comp-rises a v small terminal piece 14 mounted on arivet 15 and adapted fi'or connection to an outside-cfllrrent or theThe: rivet 15 extends through flanged insulating bushings- 16 which linethe openings provided in the lugs 2 and :arm 3 to receive the rivet 15and thebushi-ngs- 16'. The head 15* of this rivet 15 clamps the wire '11between it and the terminal piece "v14. The end-oi therivet,15-;opposite the At the split in the core v head 15 is sWaged overas at 17 against a metallic Washer 18 engaging the adjacent end of theadjacent fiber bushing 16. This construction is clearly shown in Figure3. In this way the terminal piece 14 is electrically connected with oneend foil the wire binding post 20 comprises a terminalpiece- 21 of thesame. aOOIlShIHQtlQIl. as the terminal piece 14 This terminal piece 21isclamped? between the. head 22? of a rivet .and the adjacent lug 2 ofthe core. The end of the rivet opposite the head- 22 is swa-gedoneragainst the adjacent lug 2 of the core no insulating bushings orwashersare provided between-the terminal piece :21 and-thelugs of thecore, the terminal piece .21 is electricallyconnected with the lugs ofthe core and with the arm 3 engaged with theselugs. With the arrangementdescribed,. the

current may flow from the binding-post.

through the wire 11 tothe contact shoe 9, through the-contact shoe 9toits. arbor 7.,

the. sleeve 5, the bight portion 4 of the :arm? 3,, and thenathrough thearmVB to; the lugs 2 and binding post 20; By shifting the-eontact arm9arou-nd the core more or less resistance he interposed in the circuit;

7 The arm 3 may have its sections provided with bendable lugs 24 and25,, the lugs 24 and 25 being adapted to serve as-.-stops,.;and

also as means for disengaging the contact;

shoe from the resistor.

As illustrated in Figures 1. and 4, the lu-gs24 may be bent at.-

an, angle to the arm3, While the lug 25- is,

left in the same plane as its sectionofthe arm 3. With this arrangementthe lug '25..

serves as astop for limiting the angular movement of the contact shoe:9; The vlug 24 on the other hand has its enter end roundedor beveled.off as indicated at 24 whereby to iacilitate. the beveled contact shoeriding up on tot'he lug 24; in which position the contact shoe is heldins-paced relationto the turns of the wire 11 to interrupt the circuit;

' When the device is used as a singlepoten. tiornete-r a third bindingpostLdesignated generally at 26 is provided and is mounted, on aperturedextensions 27 of the arm The binding post 26 consistsv of a terminalplate 27 mounted on a'rivet 28 and engagthe opposite end of the. Wire 11i'rom. that engaged with the terminal plate 145.

The end of the wire- 11 engaged with the terminal plate clamped betweenplate 27 and the head 28 of the rivet 28. The opposite end of the rivetis swaged over a metallic washer 29 which bears against one end of oneof a pair of flanged insulating bushings 30, the insulating bushings 30serving to insulate the rivet 28 from the ears 27* of the arm 3. Inusing the device as a potentiometer, the binding posts 13 anl 26 areincorporated in the circuit containing the source of current. Thebinding posts 20 and 26 are connected to the circuit upon which thevariable voltage is to be impressed. By shifting the contact shoe 9 thevalue of the resistance interposed between the source of current and thecircuit to be energized is varied, and consquently a variable voltage ishad.

As shown in Figure 2, the sleeve 5 has an externally threaded portion 35projecting beyond the bight portion 4 of the arm 3, and in use thisexternally threaded portion 35 may be extended through an openingprovided therefor in a panel 36. One or more nuts 37 may be threaded onthe portion 35 of the sleeve for clamping the device in position on thepanel. An operating knob 37 is suitably fixed to the portion of theshaft 7 projecting beyond the sleeve.

The device may he used as a double potentiometer by providing a secondcontact shoe 38. The contact shoe 38 has an eye 39 at its inner end, andthis eye 39 is hushed by the flange of an insulating washer 40, thewasher 4O abutting the adjacent end of the bight portion 4 of the arm 3.The opposite side of the shoe 35 is engaged by an insulating washer 41which is forced up against the shoe by nut 42 threaded on the sleeve 5.In this way the shoe is not only mounted on and insulated from thesleeve 5, but is frictionally held in any adjustment. The portion of theshoe which engages the re sistor has beveled edges 43. The outer end ofthe shoe is provided with an angular extension 44 containing anoperating knob 45. This angular extension 44 has a flexible wire 46soldered thereto whereby the shoe is connected up with theinstrumentalit-ies with which; it is associated.

The hook-up forms no part of the present invention and hence theadaptability of the device for its various connections is only generallyindicated.

It is to be noted that the same resistor presents opposite edge portionsso as to be adapted to coact with two contact shoes, thereby enablingthe use of the device as a rheostat or a single or double potentiometer.

The invention claimed is:

1. A device of the character described comprising a substantiallyannular core, insulation on the core, a resistor wrapped around thecore, contact shoes cooperable with the opposite edge portions of theresistor, and a mounting for the contact shoes supported from the core,said contact shoes being electrically insulated from each other.

2. A device of the character described comprising a substantiallyannular core, insulation on the core, a resistor wrapped around thecore, contact shoes cooperable with the opposite edge portions of theresistor, an arm directly and rigidly secured to the core, and a sleeveat the inner end of the arm for supporting the contact shoes, saidcontact shoes being electrically insulated from each other.

A device of the character described comprising a split annular core, anarm rigidly and directly secured to the core at the split, a shaftsupported by the arm, a resistor mounted on and insulated from the core,and a contact shoe mounted on the shaft and cooperable with theresistor, and two bendable lugs on the arm, one disposed to limit themovement of the contact shoe in one direction and the other disposed tolift the contact shoe out of engagement with the resistor.

4. A device of the character described comprising a sleeve, a splitannular core concentrically disposed with respect to said sleeve andhaving outturned lugs at its split, a radial connectingarm doubled uponitself and having a bight at its inner end embracing and secured to thesleeve, the outer end of the radial arm being secured between the lugsof the core, a resistor mounted on and insulated from the core, and acontact shoe mounted on the sleeve and engageable with the resistor.

5. A device of the character described comprising a sleeve, a splitannular core concentrically disposed with respect to said sleeve andhaving outturned lugs at its split, a radial connecting arm doubled uponitself and having a bightat its inner end embracing the sleeve, a weldbetween the portion of the arm adjacent the sleeve whereby the arm isfixed on the sleeve, the outer end of the radial arm being securedbetween the lugs of the core, a resistor mounted on and insulated fromthe core, and a contact shoe mounted on the sleeve and engageable withthe resistor.

6. A device of the character described comprising a split annular core,an arm rigidly and directly secured to the core at the split, a shaftcarried by the arm, a resistor mounted on and insulated from the core, acontact shoe mounted on the shaft and engageable with the resistor, andbendable lugs on the arm and engageable with the contact shoe.

7. A device of the character described comprising a split annular coreof conductive material, said core having integral outturned lugs at thesplit, an arm of conductive material having its outer end directlysecured to and between the lugs of the core,

other binding post.being ielectrically'connect-v a sleeve "of conductivematerial carried-thy the :arm ::and electrically connected 'there"wlthy. ayco-vering of insulation *on the core,

acresistor' rapped-around :the insulation: of the core; aiconta'ct shoemounted on and electrically connected with :the sleeve and engageablewith the resistor, andcbinding posts mounted-ion the lugs, one of thebinding posts being insulatedrifroin the lugs and electrically connectedwith "the "resistor, the

ed with the contact shoe through a the lugs,

arnriand sleeve.

'8. A device of 'the character described coinprisingaxsplit COIQ'fOIIDBdwith offset lugs at :its sp1it','an arm having a portion dlsposedbetween :sald lugs, a reslstor mountedon .iand insulated'from-the core,.a

shaft carried ,bythe -a'r1n,.a contact shoe mounted on the shaft andengageable Wlth the tresistor, binding posts for-thereslstor and contactshoe, and :rivets coacting with the lugs, arm and binding posts forclamping and rigidly securing thelugsto-the arm andfforz mountingtheibinding :posts in posi 7 tion on the lugs.

9. A vdevice of the character described comprising 2, "split core havingtransversely extending lugs: at its split, a resistor mounted 0n andinsuiated'from the core, a radial arm doublediuponiitself and having abight atgits inner end provided with hearing means, the outer end oftheradialarmbeing r secured between the lugs of the core, a

: shaftc'niountediin the-bearing. means OfithG arm and a contact shoemountedon'theshaft and 'engageable with the resistor. V

.In wltness Wl18I60f, I hereto *afiix nay-signature. @ERKVINTR.:STOEKLE.

ates-47242

